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At least 199 records · Page 11Linked to original sources
PubMed1999

T2-weighted MRI of the uterus: fast spin echo vs. breath-hold fast spin echo.

This study compared one routine T2-weighted fast spin echo (T2FSE) sequence with a breath-hold T2FSE (BH T2FSE) sequence of the female pelvis for image quality, uterine anatomy, lesion detection, and signal intensity measurements. Thirty-two consecutive women (mean age 41.7 years) were imaged at 1.5 T with one high-resolution routine T2FSE sequence and one BH T2FSE sequence in the sagittal plane as part of comprehensive pelvic magnetic resonance imaging. The different image sets were rated separately for imaging characteristics (overall image quality, uterine anatomy definition, lesion detection, and free fluid conspicuity) and then compared side by side. The image sets were also compared for artifacts (ghosting, blurring, pulsatility, and chemical shift misregistration). Signal-to-noise (S/N) and signal difference-to-noise (SD/N) ratios were calculated for the different uterine zones, uterine abnormalities, free fluid, rectus abdominis muscle, and bladder. Contrast-to-noise ratios (CNRs) were calculated for uterine abnormalities. Twenty-eight uterine abnormalities were detected in 20 patients and included leiomyomata (13 patients), adenomyosis (7 patients), benign endometrial polyps (6 patients), endometrial carcinoma (1 patient), and pregnancy (1 patient). BH T2FSE was superior or equivalent to T2FSE for overall image quality in 23/32 patients (71.8%), uterine anatomy definition in 19/32 patients (59.3%), and lesion detection in 13/20 patients (65%). BH T2FSE performed less well than T2FSE for free fluid conspicuity in 5/5 (100%) patients. BH T2FSE was equivalent to or less affected than T2FSE for ghosting artifact in 24/32 patients (75%) and blurring artifact in 29/32 patients (90.6%). Pulsatility and chemical shift artifacts were not problematic for either image set. S/N and SD/N were higher for all BH T2FSE determinations compared with T2FSE. For the endometrium, junctional zone, myometrium, and bladder, these differences were statistically significant. There were no statistically significant differences for CNR between the two image sets, although BH T2FSE values for leiomyomata, adenomyosis, and abnormal endometria were higher than those calculated for T2FSE. All pathology detected with T2FSE was detected on BH T2FSE despite the breath-hold sequence's inherently poorer spatial resolution compared with the non-breath-hold sequence. BH T2FSE may be able to replace T2FSE for some uterine applications with a substantial time savings.

Adult↗
PubMed1988

Identification of some abnormal haemoglobins by fast atom bombardment mass spectrometry and fast atom bombardment tandem mass spectrometry.

The characterization of two abnormal human haemoglobins by fast atom bombardment (FAB) mapping is presented. The first variant, called 'R', exhibits a tryptic FAB map identical to that of normal haemoglobin. However, using Staphylococcus protease V8, a peptide containing the carboxyl end of the beta-chain exhibits a mass shift down to 300 mass units. This clearly indicates the deletion of the two last amino acids of the beta-chain. The second variant, called 'Grenoble', is due to two different modifications of the beta-chain. The location of the Pro----Ser exchange on peptide T5 is achieved by the collisionally activated dissociation mass analyzed ion kinetic energy spectra of the corresponding [MH]+ ion. The m/z value of that peptide indicated a supplementary acid----amide modification, which was located by amino acid sequencing using chemical methods. This work concludes with the necessity of using complementary methods for achieving rapid determinations of abnormal proteins with minute amounts.

Amino Acid Sequence↗
PubMed1989

Characterization of seven antihistamines, their N-oxides and related metabolites by fast atom bombardment mass spectrometry and fast atom bombardment tandem mass spectrometry.

We have examined the synthetic N-oxides of five ethylenediamine-type antihistamines using fast atom bombardment (FAB) mass spectrometry and FAB tandem mass spectrometry (MS/MS). Fragmentation of the protonated molecule in the normal and collisionally activated spectra appeared to be characteristic for this class of antihistamine N-oxide. Spectra were also acquired from an ethanolamine and a propylamine antihistamine N-oxide for comparison. These results were very similar to those obtained from biologically produced antihistamine N-oxides, as well as isomeric metabolites, which were readily distinguished from the N-oxides by characteristic fragmentation. In addition, a prominent ion 16 daltons lower in mass, which has been attributed to loss of elemental oxygen from the protonated N-oxide in chemical ionization mass spectral studies, was shown to be a matrix-dependent product of the solution-phase reduction of the antihistamine N-oxide to the parent antihistamine during FAB ionization. These results demonstrate that with a non-reducing matrix such as glycerol, FAB mass spectrometry and FAB MS/MS are excellent methods for the characterization of the non-conjugated antihistamine metabolites such as the N-oxides.

Ethanolamines↗
PubMed1988

Fast horizontal electrophoresis. II. Development of fast automated staining procedures using PhastSystem.

The development of equipment for fast automated staining is described. It is possible to handle staining procedures with up to 20 steps and nine different solutions. To increase the reaction rate in the reaction chamber, the gels are rotated and high temperatures are used. The temperature in the reaction chamber is controlled between room temperature and 50 degrees C. Increased temperature, above 20 degrees C, generally results in faster staining and destaining. However, some reactions proceed better at a low temperature, including fixation of proteins with TCA, and the development step in silver staining, where increased temperatures cause a high background stain. Silver staining using acidic silver nitrate solution is preferred, due to easy preparation and good storage stability of the reagents. This method also causes little precipitation of silver on the walls of the reaction chamber. Silver staining is accomplished within one hour. Staining with PhastGel Blue is accomplished within 30 min.

Automation↗
PubMed2001

Ultra-fast gradient vs. fast isocratic chromatography in bioanalytical quantification by liquid chromatography/tandem mass spectrometry.

Liquid chromatography/tandem mass spectrometry (LC/MS/MS) methods developed for quantification using rapid ('ballistic') gradients on narrow bore, short HPLC columns have been previously described by this laboratory. This paper compares the fast gradient approach with the more traditional high-organic isocratic LC/MS/MS methods. The comparison is based on an analysis of the effectiveness of the chromatographic separations when using the two approaches (i.e. k', N, and W). The data presented herein are derived from actual biological samples analyzed as part of the drug discovery process.

Chromatography, High Pressure Liquid↗
PubMed2002

Implications of matrix effects in ultra-fast gradient or fast isocratic liquid chromatography with mass spectrometry in drug discovery.

In the analysis of biological samples it is important to reduce the risk of interferences from the matrix itself, other analytes, the dosing vehicle (commonly PEG), and from the MS/MS transitions used for the analysis. Rapid analysis is essential for drug discovery, and even though the requirements for separation may be minimized for speed, the integrity of the analysis is still dependent on the separation. This paper focuses on the potential for interferences from various endogenous and exogenous matrix components commonly encountered in quantitation of analytes and their metabolites from biological matrices. We demonstrate that neither high organic isocratic nor ballistic gradient ultra-fast HPLC show a clearly defined advantage in regards to complex biological matrices. The critical factor in the resolution of matrix interferences still remains in sample preparation.

Animals↗
PubMed1992

Fast spin-echo imaging of the abdomen during breath-holding: an alternative to RASE and other fast imaging techniques.

We have developed a rapidly acquired T1-weighted spin-echo pulse sequence that uses gradient echo-like parameters of TR 70 ms, TE 10 ms, NEX-1 (SE 70/10/1) with large pulse angles, and presaturation. This sequence yields two images of the abdomen during a comfortable breath-hold of 9 s. Preliminary phantom studies with this sequence demonstrated that peak signal-to-noise ratios occurred at pulse angles of 120 degrees and 135 degrees. Compared to this rapidly acquired sequence, a conventional T1-weighted spin-echo sequence of TR 140 ms, TE 10 ms, NEX-4 demonstrated 2.8 times the signal-to-noise ratio, 2.6 times the liver-spleen contrast-to-noise ratio but only 1.6 times the contrast-to-artifact ratio. When normalized for the imaging time, however, there was little difference in the signal-to-noise and contrast-to-noise ratios, although the SE 70/10/1 demonstrated 2.0 times the contrast-to-artifact ratio. We conclude that for abdominal imaging the SE 70/10/1 is an excellent alternative to RASE and other fast imaging techniques, and, although there are inherently low signal-to-noise ratios, it may be particularly useful when coupled with a paramagnetic contrast agent.

Abdomen↗
PubMed1999

Fat-suppressed fast spin-echo mid-TE (TE[effective]=34) MR images: comparison with fast spin-echo T2-weighted images for the diagnosis of tears and anatomic variants of the glenoid labrum.

OBJECTIVE: To compare the sensitivity, specificity, and accuracy of fat-suppressed fast spin-echo (FSE) mid-TE (TE[effective]=34) images with fat-suppressed FSE T2-weighted images for the diagnosis of labral abnormalities. DESIGN AND PATIENTS: The study included 27 consecutive patients who had axial fat-suppressed FSE T2-weighted and fat-suppressed FSE mid-TE MR images, and had labral abnormalities diagnosed at arthroscopy. The acquisition time was about 5 min for each sequence, but the mid-TE sequence allowed a higher spatial resolution than the T2-weighted images (256x256 versus 256x192). Twenty-eight age-matched patients with arthroscopically normal labra were included as a control group. The labrum was graded on the MR images as normal or abnormal separately by two musculoskeletal radiologists who were masked to the history and arthroscopic results. The surgical findings were used as the gold standard for calculating the sensitivity, specificity, and accuracy for interpreting the correct location of a labral abnormality. The sensitivity, specificity, and accuracy for the two sequences were compared with a McNemar test, and significance defined as P<0.05. RESULTS: For observer 1, the sensitivity for labral abnormalities was 0.59 on the T2-weighted images, and 0.78 on the mid-TE images (P=0.12). The specificity was 0.54 for the T2-weighted, and 0.64 for the mid-TE images (P=0.51). The accuracy was 0.56 for the T2-weighted, and 0.71 for the mid- TE images (P=0.08). For observer 2, the sensitivity/specificity/accuracy was 0.67/0.93/0.80 for the T2-weighted, and 0.70/0.86/0.78 for the mid-TE images (all P>0.5). CONCLUSION: In this small study there is no statistically significant difference for demonstrating labral abnormalities between FSE T2-weighted images, and higher-resolution fat-suppressed FSE mid-TE (TE[effective]=34) images obtained with a similar acquisition time. Although there was a general trend toward higher sensitivity and accuracy with the mid-TE sequence, particularly for one of the two observers, a larger study is needed to determine whether this is the preferred single axial pulse sequence for conventional MR imaging of the labrum.

Adolescent↗
PubMed1988

Continuous-flow fast atom bombardment-mass spectrometry of permethylated oligosaccharides: a comparative study of direct mixture analysis with packed capillary column liquid chromatography-fast atom bombardment-mass spectrometry.

Conventional positive fast atom bombardment (FAB) and continuous-flow FAB analysis were carried out with permethylated lacto-N-tetraose. This latter method, a new approach, has been used to analyze a mixture of permethylated oligosaccharides by liquid chromatography-mass spectrometry (LC-MS) with a packed capillary fused-silica column and the continuous-flow probe as interface. Under these conditions, we found the continuous-flow probe to be superior to the conventional probe because its low matrix level increased the signal-to-noise ratio. The analysis of the mixture of permethylated oligosaccharide alditols obtained from hen ovomucoid by LC-MS using the continuous-flow probe as interface is described.

Animals↗
PubMedDate not supplied

Abdominal applications of fast MR imaging: a comparison of fast field echo (FFE) and spin echo (SE) pulse sequences.

Fast gradient echo (GE) MR imaging during breathhold was performed in 73 abdominal MR examinations in order to determine the value of GE technique in the reduction of movement artefacts and improvement of image quality. The results were compared with conventional spin-echo (SE) technique. T1-weighted SE images consistently demonstrated normal anatomy and pathology. T2*-weighted and intermediate GE technique proved to be superior to T2-weighted SE technique in a considerable number of cases providing not only better delineation of normal structures but also better lesion detection. At this stage GE technique should be considered as an adjunct to T1-weighted SE technique. If the artefacts presently inherent to GE imaging could be reduced or compensated for, this technique of rapid MR imaging during suspended respiration could become an important tool being one of the fastest techniques for abdominal MR imaging.

Abdomen↗
PubMed1993

[CT and MRI in tumors of the mouth and oropharynx--comparison of methods with reference to fast and ultra-fast MR pulse sequences].

A total of 488 patients with neoplasms (in 474 cases with malignant tumours) of the oropharynx, floor of the mouth and oral cavity, were examined with MRI and CT. MRI proved superior to CT, on account of its coronal and sagittal slice orientation enabling not only a better demonstration of findings, but also improved tumour detection and staging. The diagnostic value of MRI was further enhanced with additional fast and ultrafast MR sequences rather than spin echo sequences alone, as previously practised.

Adenocarcinoma↗
PubMed1993

[Reduction of MRT time in the female pelvis using T2-weighted Fast-Spinecho(FSE)-technique. A quantitative and qualitative comparison of conventional spinecho(SE) and Fast-Spinecho(FSE)-sequence].

The fast spin echo (FSE) technique leads to time saving by individual phase coding of several spin echoes within one repetition interval. The new sequencing was compared quantitatively and qualitatively with conventional spin echo sequences in 30 patients with gynaecological pelvic disease. The signal-to-noise ratio was higher on FSE images in all tissues but to a variable degree. This led to an increased contrast-to-noise ratio, particularly between fat and solid structures, and to a reduction in the contrast between fat and fluid. Artifacts were reduced in FSE sequences leading to improved image quality in 83% and increased diagnostic information in 10%. This is of particular advantage when using time consuming T2-weighted sequences, which are necessary for the examination of the female pelvis.

Adult↗
PubMed2006

Fast and accurate determination of the Wigner rotation matrices in the fast multipole method.

In the rotation based fast multipole method the accurate determination of the Wigner rotation matrices is essential. The combination of two recurrence relations and the control of the error accumulations allow a very precise determination of the Wigner rotation matrices. The recurrence formulas are simple, efficient, and numerically stable. The advantages over other recursions are documented.

Journal Article↗
PubMed1997

GRASE: ultra-fast turbo gradient spin-echo sequence. A new approach to fast MR imaging of the musculoskeletal system.

PURPOSE: Ultra-fast gradient and spin-echo (GRASE) imaging is a hybrid of turbo spin-echo (TSE) and echo-planar imaging (EPI). One scan consists of several spin echoes (SEs) (turbo factor, TF), each of which consists of a number of gradient echoes (EPI factor, EF). The aim of our study was to evaluate different combinations of TF and EF in GRASE imaging and to test its usefulness in musculoskeletal imaging. MATERIAL AND METHODS: On a 1.0 T MR unit, 11 GRASE sequences with different combinations of TF and EF (TR/TE 2150/120 ms) were evaluated in phantom studies with respect to signal-to-noise (S/N) ratio, nonuniformity of images, and geometrical distortion. From this study, the optimal GRASE-sequence was applied to 25 patients with different joint pathologies and compared to a T2-weighted TSE sequence (TR/TE 2855/130 ms). Lesion visualization, conspicuity, overall image quality, and artifacts were qualitatively analyzed by two observers independently of each other. RESULTS: With respect to S/N ratio, signal nonuniformity, and geometrical distortion, the GRASE sequence with TF/EF 7/3 (S/N 47; signal nonuniformity 11.7%; distortion 1 pixel) proved to be superior to the other GRASE sequences within a scanning time of less than 120 s. In a clinical study, the GRASE sequence proved superior to T2-weighted TSE (without fat suppression) in the visualization of bone-marrow and soft-tissue lesions (p < 0.001) and ligamentous injuries, although the image quality was inferior.

Artifacts↗
PubMed2006

Habitat selection by chironomid larvae: fast growth requires fast food.

1. Sediments have been considered as a habitat, a cover from predators and a source of food, but also as a source of potential toxic compounds. Therefore, the choice of a suitable substrate is essential for the development of chironomids. 2. For the midge Chironomus riparius (Meigen 1804) the growth rate of larvae has often been related to the food quality in sediments rather than to the amount of toxicants in the sediment. Both food quality and sediment-bound toxicants have been reported to determine the field distribution of chironomid larvae. 3. We therefore studied the habitat selection by C. riparius larvae of floodplain lake sediments, differing in both food quality and concentrations of sediment-bound toxicants. We offered the different sediments pairwise to the chironomid larvae in a choice experiment and their settlement in the paired sediments was determined after 10 days. 4. It was observed that larvae showed a clear preference for sediments with higher food quality, which also provided better growth conditions, and that the food quality overruled avoidance of the sediments with higher toxicant concentrations. 5. Our observations correspond with the persistence of this fast growing opportunistic chironomid species in organically enriched aquatic ecosystems independent of the contamination level.

Animal Feed↗
PubMed2002

High-fat high-energy feeding impairs fasting glucose and increases fasting insulin levels in the Göttingen minipig: results from a pilot study.

High-fat diet and obesity are known to be of major importance for development of type 2 diabetes in humans. High-fat feeding can induce syndromes of glucose intolerance and/or insulin resistance in several species, and the Göttingen minipig might be a useful model for studying the effect of dietary high-fat intake and obesity on glucose homeostasis and the susceptibility to diabetes. The present study was designed as a pilot study to investigate the effects of obesity caused by high-fat high-energy feeding on oral and intravenous glucose tolerance. Male Göttingen minipigs were fed a control diet (CD) or a high-fat high-energy diet (HFD) for 3 months. Body weight (32.6 +/- 2.4 kg vs. 24.9 +/- 0.5 kg, p < 0.001) and total (13.2 +/- 3.2% vs. 6.1 +/- 0.5%, p = 0.002) and truncal (11.0 +/- 3.9% vs. 1.8 +/- 1.1%, p = 0.001) fat percent were increased significantly, whereas relative lean body mass was decreased (84.8 +/- 3.3% vs. 91.9 +/- 0.5%, p = 0.002) in the HFD group compared to CD. Fasting plasma glucose (4.3 +/- 0.4 mM vs. 3.6 +/- 0.3 mM, p = 0.023) and insulin (80 +/- 23 pM vs. 23 +/- 21 pM, p = 0.012) were increased in the HFD group compared to CD, but oral glucose tolerance was not significantly changed. Insulin responses to intravenous glucose were increased (6741 +/- 2538 vs. 3938 +/- 771 pM 3 min, p = 0.050), while glucose clearance was not changed by HFD vs. CD, thus indicating insulin resistance. In conclusion, changes in body weight and composition, resulting in minor abnormalities in glucose tolerance and insulin sensitivity, characterized by slight hyperglycemia and compensatory hyperinsulinemia, can be induced in the male Göttingen minipig by high-fat high-energy feeding for 3 months. This approach seems to be an interesting and promising method for establishment of a nonrodent model of insulin resistance or type 2 diabetes.

Absorptiometry, Photon↗
PubMed2005

Fast ligation-mediated PCR, a fast and reliable method for IS6110-based typing of Mycobacterium tuberculosis complex.

IS6110 restriction fragment length polymorphism (RFLP) analysis is the most widely applied method for strain differentiation of Mycobacterium tuberculosis complex. We have previously described mixed-linker PCR, an IS6110-based PCR method that favorably compared with other typing methods for M. tuberculosis complex according to reproducibility and ability to differentiate between strains. Here we report the further development of this method, called fast ligation-mediated PCR (FLiP), which allows analysis of strains within one working day and starting from less than 1 ng of mycobacterial DNA or a crude cell lysate. Blinded analysis of a standard set of 131 M. tuberculosis complex and nontuberculous isolates showed the ability to differentiate 81 types among 90 M. tuberculosis complex isolates with 84 different IS6110 RFLP fingerprint patterns and detected 97% of the 31 duplicate samples. We suggest that FLiP can serve to rapidly detect chains of transmission prior to starting high-throughput analysis or standard IS6110 RFLP. It may as well serve as a secondary typing technique for other, non-IS6110-based methods.

Bacterial Typing Techniques↗
PubMed1987

Alveolar sampling and fast kinetics of tetrachloroethene in man. II. Fast kinetics.

Fast kinetic phenomena were studied in human subjects exposed to tetrachloroethene (perchloroethylene, PER). The duration of exposure ranged from one to 60 minutes and the concentration of PER in inhaled air ranged from 0.02 to 0.40 mmol/m3. The PER concentration in mixed venous blood (pulmonary artery) was estimated by alveolar concentration (CAlv) measured after a residence time of 10 s. During exposure, stoppage of intake (breath holding up to 50 s) caused a decrease of CAlv down to about 60% of the CAlv at a residence time of 10 s. At the end of exposure, stoppage of intake (breathing fresh air) caused a decrease of CAlv with t1/2 = 15-25 s; after two to four minutes, the decrease slowed down abruptly and the concentration remained more or less constant for about one to three minutes. After this stationary level, the decrease of CAlv continued but at a slower rate. During and after exposure, the decrease of CAlv seems to be caused by large differences in the circulation times of blood flowing through rapid, well perfused tissues and slower, well perfused tissues which may explain the stationary level. From this point of view, the vessel rich group in a compartment model must be split up in order to predict tissue and organ concentrations during peak environmental concentrations.

Blood Volume↗